Modelling open channel flow for the features of a flexible groyne: Effects of permeability and head steepness of groynes on local flow characteristics

Large-scale measures within the river programmes such as Room for the River, Natura2000 and Water Framework Directive have increased the biodiversity in Dutch rivers and have achieved a more natural landscape. However, recent river programmes have shown conflicts between safety against flooding and riverine nature rehabilitation with maintaining...

Direct numerical simulation of two-phase stratified flows in the primary coolant of a nuclear reactor

Multiphase flows are very common in many Nuclear engineering applications. During high pressurized conditions there are possibilities of high thermal loads on the pressure vessel, leading to pipe ruptures. As part of breakdown measures, the emergency core cooling system is activated and the coolant is mixed with the fluid in the cold leg, giving...

Approximate basis and a priori closure models for energy-conserving reduced order modeling of fluid flows

Model order reduction (MOR) has been a field of active research in the past twenty years, more recently also in fluid dynamics. The main advantage of MOR is computational cost reduction, which, along with equally important accuracy, constitute main objective in the MOR community.<br/>A main ongoing issue is that data volumes in fluid flow...

Frozen-RANS Turbulence Model Corrections for Wind Turbine Wakes in Stable, Neutral and Unstable Atmospheric Boundary Layers

Computational Fluid Dynamics based on RANS models remain the standard but suffer from high errors in complex flows. In particular, turbulent kinetic energy is over-produced in high strain rate regions, such as the near wake of wind turbine flows. Data-driven turbulence modelling methods aim to derive novel turbulence models with lower...

Rotating Discs Actuators: Direct Numerical Simulation for Turbulent Skin­Friction Drag Reduction

In the aviation, maritime and oil&amp;gas sector, the potential benefit in yearly savings deriving from the reduction of turbulent skin-friction drag through active flow control are estimated in the millions of U.S. Dollars and million tonnes of CO2 emissions. Research in this topic has brought forward numerous techniques, offering enticing drag...

Modelling of wall-bounded flows near a cylinder-bed junction in turbulent flow conditions using an IDDES turbulence model to asses initial particle entrainment

Due to the presence of a monopile in a turbulent flow swirling vortices, known as horseshoe vortices, can form upstream of the structure near the cylinder-bed junction. Those vortices then travel downstream of the cylinder as they are being dragged along with the current. The horseshoe vortices can scoop up bed material surrounding the cylinder,...

Numerical investigation of nearshore wave transformation and surf zone hydrodynamics

Rapid climate change and the corresponding estimated sea level rise can affect the performance of the coastal defense structures such as breakwaters, seawalls, and dikes. In order to improve these coastal defenses, a detailed understanding of the processes which contribute to wave run-up and overtopping over the coastal defenses needs to be...

Development of a transient CFD methodology for the optimization of CNG engines

Compressed natural gas (CNG) has been gaining attention in the automotive industry since it allows for a substantial reduction in carbon dioxide emissions. Recent advancements in direct-injection technology have contributed to an increase in volumetric efficiency and engine power, but the physical modeling of such gaseous injection with...

Multi-fidelity Co-Kriging Optimization using Hybrid Injected RANS and LES

The computation of complex turbulent flows design optimization processes is currently limited by the lack of accuracy of Reynolds-Averaged Navier-Stokes (RANS) in massively separated flows and the infeasible cost of multiple Large-Eddy Simulation (LES) evaluations. A novel method is presented, injecting data from LES or other high-fidelity...

Micro-Ramp Flow Dynamics

Micro-ramps are passive flow control devices used to delay flow separation. Their use is widespread due to their reduced drag and structural robustness. We reproduce with Direct Numerical Simulations (DNS) recent Particle Image Velocimetry (PIV) experiments of the micro-ramp flow performed at TU Delft to study the wake of a micro-ramp immersed...

Extending a RANS Solver with heat and pollution modules for dispersion problems in urban areas with vegetation

Currently, 54% of the general population lives in urban areas. This number is estimated to increase to 66% by 2050. Urbanization is generally linked to several phenomena that are detrimental to the overall quality of life; the urban heat island effect, and the decrease of air quality due to pollutants. The addition of vegetation to urban areas...

Turbulence in Aneurysms: Numerical Investigation in Abdominal Aortic Aneurysms

An aneurysm refers to the local dilation or ballooning of a blood vessel and if left unchecked, almost every aneurysm continues to grow in size until it eventually ruptures. The abdominal aorta is the most common location for an aneurysm to form and an abdominal aortic aneurysm (AAA) can turn lethal in the event of rupture. Since the current...

DNS study of scalar transport in a compressible turbulent jet

Direct Numerical simulations (DNS) belong to the class of simulations that strive to emulate the real physical flow by trying to simulate the complete range of scales involved in the flow. Though the computational power has steadily increased in the past few decades, resolving the complete range of scales from the largest scales up to the...

Time-Supersampling 3D-PIV Measurements by Vortex-in-Cell Simulation

Measurement rate limitations of time-resolved 3D-3C velocity measurements by tomographic PIV limit application of the technique to small measurement volumes and low speed flows (~10 m/s). To reduce the challenging repetition rate requirements historically set by the Nyquist criterion, in the present thesis work a novel method is proposed,...